On Wed, 29 Sep 2010 11:55:21 -0400
"Roger K. Wells" <ROGER.K.WELLS(a)saic.com> wrote:
I have a RS485 serial device (Quatech SSU2-300) that when plugged
into a USB (2.0) port appears to be recognized correctly. dmesg yields:
cp210x 3-1:1.0: cp210x converter detected
usb 3-1: reset full speed USB device using uhci_hcd and address 8
usb 3-1: cp210x converter now attached to ttyUSB0
A "C" language program attempting to use this port hangs at the
open call.
This same program with the same device worked on a Centos 5.5
install on the same computer.
uname -r : 2.6.34.7-56.fc13.x86_64
The USB device works in Windows XP so I don't think there is a defect
there.
Modern kernels properly handle carrier detect and wait so open it with
O_NDELAY if you don't want to wait for the carrier line to be asserted
and/or set the CLOCAL termios bits if you are not using the carrier and
flow control.